An inkjet head of one type includes a plurality of piezoelectric elements arranged along a line and a plurality of pressure chambers, each arranged between two adjacent piezoelectric elements. In order to stabilize pressure of liquid in the pressure chambers and more reliably discharge the liquid in the pressure chambers, wall of the pressure chamber may be formed of a rigid material. To achieve such an objective, a lid member having a high rigidity may be bonded to the piezoelectric elements to form walls of the pressure chambers.
One method for bonding the lid member to the piezoelectric elements employs a thermosetting material. However, as the lid member has rigidity, an internal stress may remain in the piezoelectric elements after heat is applied for bonding and the thermosetting material is cooled off. When the piezoelectric elements are subjected to the internal stress, the liquid in the pressure chambers may not be properly discharged.